A device of this type is known from DE 10 2005 012 265 A1.
The prior-art device is used for bonding and structuring fiber layers. For this purpose, a fibrous web is pierced with a plurality of needles, which are guided in an oscillating motion. In the process, the needles are thus guided with an oscillating vertical motion in order to bond the fibrous material in the fibrous web. In this process, the fibrous web is constantly moved forwards with a feed, which is preferably performed by rollers. Since the needles are not smooth, but are provided with barbs open in the puncture direction, individual fibers are grasped during the puncturing and reoriented within the fiber layer. Consequently, a felting and bonding effect is achieved. To not obtain any undesired deformations that lead, for example, to a drawing or a slot formation in the needled material during the puncturing of the needles in the fibrous web because of the feed of the fibrous web, the needles are guided with superimposed horizontal motion, which takes place superimposed on the vertical motion.
In the prior-art device, both the vertical motion and horizontal motion of the needle bar are initiated by means of a crankshaft assembly at the needle bar. The crankshaft assembly has two crank drives with two driven crankshafts for this purpose. The crankshafts are designed as adjustable in their phase positions by means of a phase-adjustment means. Depending on the phase position of the crankshafts to one another, an ellipse-like pattern of motion, in which the oscillating motion of the needle bar is carried out, is produced. To obtain an as stable as possible puncturing of the needles in the fibrous web, a guide means which acts on the needle bar is additionally provided. However, both the vertical motions of the needle bar and the horizontal motions of the needle bar should be performed unobstructed. In the prior-art device, the guide means is formed by a guide rod which is guided in a guide sleeve held on a machine frame. The guide sleeve is held on the machine frame pivotably via a pivot bearing, such that, depending on the phase position of the crankshafts, an oblique positioning of the bar carrier via the pivot bearing of the guide means is possible. In this case, during the drive of the bar carrier, the guide path performed by the bar carrier is essentially dependent due to the fixed position of the pivot bearing of the guide means. Thus, only very small horizontal strokes can be made by a phase adjustment of the crankshafts.
Further, in the prior-art device, the problem arises that with increasing degree of phase adjustment between the two crankshafts, the free forces due to inertia and moments of inertia increase and lead in the extreme case to increased vibrations in the machine frame. Horizontally directed forces due to inertia are especially produced by the horizontal motion component of the needle bar, which can be balanced only insufficiently by means of a mass balancing at the crankshafts. In this respect, the prior-art device is only suitable for performing a horizontal motion of the needle bar within narrow limits.
However, such devices, in which the vertical motion of the needle bar is performed by a vertical drive and the horizontal motion is performed by a separate horizontal drive, are basically known in the state of the art. Such a device is known, for example, from DE 197 30 532 A1. The separate horizontal drive of the prior-art device makes possible even greater motion amplitudes, but with the drawback of complicated mechanisms, which limit the stroke frequency of the machine and with a high space requirement lead to large and heavy machine frames.